Methods of forming an integrated circuit capacitor in which a metal preprocessed layer is formed on an electrode thereof

ABSTRACT

An integrated circuit capacitor is manufactured by forming a lower electrode on a substrate and forming a metal preprocessed layer on the lower electrode using chemical vapor deposition in which a metal precursor is used as a source gas and the metal precursor comprises oxygen. A dielectric layer is then formed on the metal preprocessed layer and an upper electrode is formed on the dielectric layer. The metal preprocessed layer may reduce oxidation of the lower electrode due to oxygen supplied during formation of the dielectric layer.

RELATED APPLICATION

[0001] This application claims the benefit of Korean Patent ApplicationNo. 2001-2960, filed Jan. 18, 2001, the disclosure of which is herebyincorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates generally to methods ofmanufacturing integrated circuit devices and, more particularly, tomethods of manufacturing integrated circuit capacitors.

BACKGROUND OF THE INVENTION

[0003] As integration density of integrated circuit devices increases,use of a dielectric layer having a high dielectric constant may be usedto obtain high capacitance in a small space. The high dielectricconstant material may be Ta₂O₅, TiO₂, A1 ₂O₃, Y₂O₃, ZrO₂, HfO₂, BaTiO₃,or SrTiO₃.

[0004] Although these oxide layers have a relatively high dielectricconstant, they may react with polysilicon, which is a material commonlyused as a lower electrode in conventional capacitors. For example,polysilicon may be oxidized by reacting with a tantalum oxide layerduring a process of forming the tantalum oxide layer or during a thermaltreatment process after formation of the tantalum oxide layer. To reduceoxidation, a nitride layer may be interposed between the tantalum oxidelayer and the polysilicon and used as a barrier layer against diffusionof oxygen.

[0005] Another approach to reducing oxidation involves forming a lowerelectrode of a material that is relatively difficult to oxidize. Forexample, a noble metal, such as Pt, Ru, Ir or a conductive metalnitride, such as TiN may be used. FIG. 1 illustrates a Ru layer 110 thatis formed on a silicon substrate 100 and thermally treated in an ozone(O₃) atmosphere at 250° C. As shown in FIG. 1, columnar crystal phases120 exist on the surface of the Ru layer 110. These columnar crystalphases 120 are RuO₂, which is formed by oxidization of the Ru layer 110due to ozone. These RuO₂ crystal phases 120 may inhibit formation of thedielectric layer (e.g., a tantalum oxide layer) and also deteriorate theproperties of the capacitor by reducing the contact area between the Rulayer 110 and the dielectric layer. In particular, when the dielectriclayer is formed on a substrate having a cylindrical opening, such as,for example, an opening for a cylindrical capacitor, the dielectriclayer may not be formed on lower portions of the opening. As a result,step coverage of the dielectric layer may deteriorate.

SUMMARY OF THE INVENTION

[0006] According to embodiments of the present invention, an integratedcircuit capacitor is manufactured by forming a lower electrode on asubstrate and forming a metal preprocessed layer on the lower electrodeusing chemical vapor deposition in which a metal precursor is used as asource gas and the metal precursor comprises oxygen. A dielectric layeris then formed on the metal preprocessed layer and an upper electrode isformed on the dielectric layer. The metal preprocessed layer may reduceoxidation of the lower electrode due to oxygen supplied during formationof the dielectric layer.

[0007] In other embodiments of the present invention, the lowerelectrode comprises polysilicon, a noble metal, and/or a metal nitride.

[0008] In still other embodiments of the present invention, the metalprecursor comprises Ta(OCH₂H₅)₅ or Ta(OCH₃)₅.

[0009] In still other embodiments of the present invention, the metalpreprocessed layer is formed by placing the substrate into a reactionchamber, adsorbing the metal precursor in the lower electrode, reactingthe metal precursor with the lower electrode, and purging the metalprecursor from the reaction chamber.

[0010] In further embodiments of the present invention, the dielectriclayer comprises a metal oxide layer, which is formed by placing thesubstrate into a reaction chamber, introducing a metal source gas intothe reaction chamber, adsorbing the metal source gas in the lowerelectrode, purging the metal source gas from the reaction chamber,introducing an oxygen source gas into the reaction chamber, adsorbingthe oxygen source gas in the lower electrode, and reacting the adsorbedmetal source gas with the adsorbed oxygen source gas.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Other features of the present invention will be more readilyunderstood from the following detailed description of specificembodiments thereof when read in conjunction with the accompanyingdrawings, in which:

[0012]FIG. 1 illustrates a Ru layer that is formed on a siliconsubstrate and thermally treated in an ozone (O₃) atmosphere;

[0013]FIG. 2 is a flow chart that illustrates methods of forming anintegrated circuit capacitor in which a metal preprocessed layer isformed on an electrode thereof in accordance with embodiments of thepresent invention;

[0014]FIG. 3 illustrates a section of a Ru layer, which has a tantalumpreprocessed layer formed thereon in accordance with embodiments of thepresent invention;

[0015]FIG. 4A illustrates a section of a tantalum oxide layer formed ona Ru layer having a tantalum preprocessed layer formed thereon inaccordance with embodiments of the present invention; and

[0016]FIG. 4B illustrates a section of a tantalum oxide layer formed ona Ru layer without a tantalum preprocessed layer formed thereon.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0017] While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Itshould be understood, however, that there is 30 no intent to limit theinvention to the particular forms disclosed, but on the contrary, theinvention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theclaims. Like numbers refer to like elements throughout the descriptionof the figures.

[0018]FIG. 2 is a flow chart that illustrates operations for forming anintegrated circuit capacitor in accordance with embodiments of thepresent invention. Operations begin at block 201 where a lowerelectrode, which comprises polysilicon, a noble metal, and/or a metalnitride is formed on an integrated circuit substrate. The noble metalmay be Ru, Pt, or Ir. The metal nitride may be a single metal nitride,such as TiN, or a nitride comprising more than two metals, such as (Ti,Ta)N. The noble metal and the metal nitride may be deposited usingchemical vapor deposition (CVD).

[0019] Next, a tantalum preprocessed layer is formed on the lowerelectrode at block 202. The tantalum preprocessed layer may be formedusing CVD in which a metal precursor having a tantalum-oxygen bond isused as a source gas. The tantalum precursor having an oxygen bond maybe Ta(OCH₂H₅)₅ and/or Ta(OCH₃)₅. In accordance with other embodiments ofthe present invention, another metal preprocessed layer may be usedinstead of the tantalum preprocessed layer. For example, a titanium (Ti)preprocessed layer may be formed using a precursor such as TiO(DPM)₂and/or Ti(t-BuO)₂(DPM)₂, and a zirconium (Zr) preprocessed layer may beformed using a precursor such as Zr(OBu^(t))₄.

[0020] The tantalum preprocessed layer may be formed by general thermalCVD, atomic layer deposition, and sequential layer deposition using thetantalum precursor as a source gas. Atomic layer deposition is a type ofCVD that involves chemisorbing a flowed source gas on the surface of asubstrate, purging the remnant source gas, and forming a material layercomprising the chemisorbed source gas. The material layer may be formedto a desired thickness by repeating the cycle of inflow of the sourcegas and purging. Because the thickness of the material layer may becontrolled at atomic layer unit precision, it may be possible to form amaterial layer having relatively good step coverage. Also, the densityof impurities contained in the material layer may be relatively low.Sequential layer deposition may comprise atomic layer deposition alongwith forming a plurality of atomic layers during a cycle by controllingthe flow rate of the source gas and the pressure of the reaction chamberso that the source gas may be chemically and physically adsorbed on thesubstrate. Hereinafter, atomic layer deposition is used in a broad senseto include sequential layer deposition.

[0021] For a capacitor having a three-dimensional structure, such as acylindrical capacitor, atomic layer deposition may be used to uniformlyform the tantalum preprocessed layer. Operations for forming a tantalumpreprocessed layer, in accordance with embodiments of the presentinvention, will now be described in greater detail. An integratedcircuit substrate having a lower electrode formed thereon that comprisesa noble metal or a metal nitride is introduced into a reaction chamber.Next, a tantalum precursor, which includes oxygen as a source gas forforming a preprocessed layer, is introduced into the reaction chamber.The introduced tantalum precursor is chemically or physically adsorbedin the lower electrode and substrate. A purge gas is then introducedinto the reaction chamber to purge the source gas remaining within thereaction chamber. The operations of introducing the source gas andpurging are repeated to uniformly form the tantalum preprocessed layeron the lower electrode. The number of repetitions of the cycle can becontrolled depending on the shape of the capacitor. For example, for acylindrical capacitor that includes a cylindrical lower electrode havinga high aspect ratio, it may be desirable to increase the number ofrepetitions of the cycle to uniformly form the tantalum preprocessedlayer on the entire lower electrode.

[0022] The tantalum preprocessed layer reacts with oxygen included inthe precursor to form an oxide layer. The rate of formation of the oxidelayer is typically relatively low because oxidation is performed usingonly oxygen included in the tantalum precursor and not using anadditional oxygen source. Even if the number of repetitions of the cycleis increased, however, the resultant thickness of the preprocessed layermay not change very much.

[0023] In accordance with embodiments of the present invention, the flowrate of the tantalum precursor during the deposition process may beabout 1-2000 sccm. The purge gas may be nitrogen or argon, and the flowrate may be about 1-2000 sccm. The temperature of the reaction chambermay be maintained to be in a range of about 100-600° C., and thepressure of the reaction chamber may be maintained at about 0.1-30 torr.

[0024] After the tantalum preprocessed layer is formed, a tantalum oxidelayer is formed on the tantalum preprocessed layer at block 203. Thetantalum oxide layer may be formed by general thermal CVD or atomiclayer deposition. The tantalum source gas for forming the tantalum oxidelayer may be Ta(OCH₂H₅)₅, Ta(OCH₃)₅, and/or TaCl₅, and the oxygen sourcegas may be H₂O, H₂O₂, O₂, N₂O, O₃, or a mixture of these gases.

[0025] For a capacitor having a three-dimensional structure, such as acylindrical capacitor, it may be desirable to use atomic layerdeposition to increase step coverage of the tantalum oxide layer.Exemplary operations for forming the tantalum oxide layer will now bedescribed. First, the integrated circuit substrate on which the tantalumpreprocessed layer is formed is introduced into the reaction chamber,and the tantalum source gas is introduced into the reaction chamber tobe adsorbed on the substrate. After a predetermined time has passed, thetantalum source gas within the reaction chamber is purged, and theoxygen source gas is introduced into the reaction chamber to be adsorbedon the substrate. Next, the adsorbed tantalum source gas reacts with theadsorbed oxygen source gas to form the tantalum oxide layer.

[0026] In accordance with embodiments of the present invention, the flowrate of the tantalum precursor during the deposition process may beabout 1-2000 sccm and the flow rate of the oxygen source gas may beabout 1-2000 sccm. The purge gas may be nitrogen or an inert gas, suchas argon, and the flow rate may be about 1-2000 sccm. The temperature ofthe reaction chamber may be maintained to be in a range of about100-600° C., and a pressure of the chamber may be maintained to be about0.1-10 torr.

[0027] Referring now to FIG. 2, an upper electrode is formed on theintegrated circuit substrate on which the tantalum oxide layer is formedat block 204. The upper electrode may be a polysilicon layer, a metalnitride layer, such as TiN formed by CVD or atomic layer deposition, anoble metal layer, such as Ru, Ir, Pt, or a composite layer thereof.

EXAMPLE 1

[0028] The following example illustrates effects of preventing oxidationof a tantalum preprocessed layer in accordance with embodiments of thepresent invention.

[0029] After three flat silicon substrates were prepared, TEOS layerswere formed on each of the silicon substrates, and Ru layers were formedon each of the TEOS layers to a thickness of about 300 Å. Next, tantalumpreprocessed layers were formed on the Ru layers using Ta(OC₂H₅)₅ as atantalum precursor. The tantalum preprocessed layers were formed byrepeating a cycle of flowing Ta(OC₂H₅)s followed by purging using atomiclayer deposition as described above. The cycle was repeated 10 times forone substrate, 100 times for another substrate, and 200 times for athird substrate.

[0030] Next, the temperature of the reaction chamber was maintained tobe about 250° C., and O₃ was flowed as an oxygen source on each of theintegrated circuit substrates on which the preprocessed layer wasformed. The Ru layers formed on each of the silicon substrates wereoxidized, and sections of the integrated circuit substrates wereobserved with a scanning electron microscope (SEM). It was not possibleto observe formation of RuO₂ on each of the Ru layers regardless of thenumber of repetitions of the cycle. For example, an SEM picture of asection of the substrate on which the cycle was repeated 100 times isillustrated in FIG. 3. The surface of the Ru layer 220 formed on theTEOS layer 210 of the silicon substrate 200 is relatively smooth, and,in contrast to the prior art example discussed above with reference toFIG. 1, a columnar RuO₂ layer is not formed on the surface of the Rulayer 220. The thickness of the preprocessed layer (not shown), whichwas formed on the surface of the Ru layer 220, was relatively thin(about 10 Å).

EXAMPLE 2

[0031] The following example illustrates that a dielectric layer havingrelatively good step coverage may be formed on a cylindrical lowerelectrode when the lower electrode comprises, for example, a tantalumpreprocessed layer disposed on a Ru layer in accordance with embodimentsof the present invention.

[0032] A TEOS insulating layer was formed and patterned on a siliconsubstrate to form a cylindrical opening having an aspect ratio of about15. A Ru layer was formed on the insulating layer and a tantalumpreprocessed layer was formed on the Ru layer by atomic layer depositionin which Ta(OC₂H₅)₅ was used as a source gas. The cycle of flowing thetantalum precursor gas followed by purging was repeated 100 times toform the preprocessed layer. Next, a tantalum oxide layer was formed onthe resultant substrate at about 250° C. by atomic layer depositionusing Ta(OC₂H₅)₅ as a tantalum source gas and O₃ as an oxygen sourcegas. A section of an opening formed on the substrate was observed with aSEM.

[0033] The operations described above for forming the TEOS layer,patterning the opening, forming the Ru layer, and forming the tantalumoxide layer were repeated on another substrate, but the tantalumpreprocessed layer was not formed. A section of an opening formed on thesubstrate was also observed with the SEM.

[0034]FIGS. 4A and 4B illustrate typical SEM pictures of sections ofopenings formed on the substrate that underwent a process for formingthe tantalum preprocessed layer and the substrate that did not undergo aprocess for forming the tantalum preprocessed layer, respectively. InFIGS. 4A and 4B, the same reference numerals represent the sameelements.

[0035] Referring now to FIG. 4A, a tantalum preprocessed layer 330 on aRu layer 310 allows a tantalum oxide layer 340 to be uniformly formed onan upper portion and a lower portion of an opening 350. On the otherhand, referring now to FIG. 4B, the tantalum oxide layer 340 is notformed on lower portions of the opening 350. This is because columnarRuO₂ crystals 320 inhibit formation of the tantalum oxide layer 340. TheTEOS layer is represented by reference numeral 300.

[0036] Thus, according to embodiments of the present invention, in anintegrated circuit capacitor having a metal oxide layer as a dielectriclayer, oxidation of a lower electrode due to oxygen supplied duringformation of the metal oxide layer may be reduced by forming a metalpreprocessed layer on a lower electrode of a polysilicon layer, a noblemetal layer, or a metal nitride layer. In particular, in a capacitorhaving a three-dimensional structure and a large aspect ratio,deterioration of step coverage of the metal oxide layer, which may becaused by failure of the metal oxide layer to form on an oxidizedportion of the electrode, may be reduced by uniformly forming the metaloxide layer on the surface of the lower electrode.

[0037] In concluding the detailed description, it should be noted thatmany variations and modifications can be made to the preferredembodiments without substantially departing from the principles of thepresent invention. All such variations and modifications are intended tobe included herein within the scope of the present invention, as setforth in the following claims.

We claim:
 1. A method of forming an integrated circuit capacitor,comprising: forming a lower electrode on a substrate; forming a metalpreprocessed layer on the lower electrode using chemical vapordeposition in which a metal precursor is used as a source gas and themetal precursor comprises oxygen; forming a dielectric layer on themetal preprocessed layer; and forming an upper electrode on thedielectric layer.
 2. The method of claim 1, wherein the lower electrodecomprises at least one material selected from a group of materialsconsisting of polysilicon, a noble metal, and metal nitride.
 3. Themethod of claim 2, wherein the noble metal is selected from a group ofnoble metals consisting of Ru, Pt, and Ir.
 4. The method of claim 2,wherein the metal nitride is selected from a group of metal nitridesconsisting of titanium nitride, tantalum nitride, and tungsten nitride.5. The method of claim 1, wherein the metal precursor comprises Ta. 6.The method of claim 1, wherein the metal precursor comprises a materialselected from a group of materials consisting of Ta(OCH₂H₅)₅ andTa(OCH₃)₅.
 7. The method of claim 1, wherein forming the metalpreprocessed layer comprises: placing the substrate into a reactionchamber; adsorbing the metal precursor in the lower electrode; reactingthe metal precursor with the lower electrode; and purging the metalprecursor from the reaction chamber.
 8. The method of claim 7, wherein aflow rate of the metal precursor during deposition is about 1-2000 sccm.9. The method of claim 7, wherein a temperature in the reaction chamberis about 100° C.-600° C.
 10. The method of claim 7, wherein purging themetal precursor comprises purging the metal precursor from the reactionchamber using a purge gas selected from a group of purge gasesconsisting of argon and nitrogen.
 11. The method of claim 7, wherein apressure in the reaction chamber is about 0.1-30 torr.
 12. The method ofclaim 1, wherein the dielectric layer comprises a metal oxide layer. 13.The method of claim 12, wherein forming the metal oxide layer comprises:placing the substrate into a reaction chamber; introducing a metalsource gas into the reaction chamber; adsorbing the metal source gas inthe lower electrode; purging the metal source gas from the reactionchamber; introducing an oxygen source gas into the reaction chamber;adsorbing the oxygen source gas in the lower electrode; and reacting theadsorbed metal source gas with the adsorbed oxygen source gas.
 14. Themethod of claim 13, wherein the metal oxide layer comprises tantalumoxide.
 15. The method of claim 13, wherein the metal source gascomprises a source gas selected from a group of source gases consistingof Ta(OCH₂H₅)₅, Ta(OCH₃)₅, and TaCl₅
 16. The method of claim 13, whereinthe oxygen source gas comprises at least one source gas selected from agroup of source gases consisting of H₂O, H₂O₂, O₂, N₂O, and O₃.
 17. Themethod of claim 13, wherein a flow rate of the metal source gas and aflow rate of the oxygen source gas during deposition is about 1-2000sccm.
 18. The method of claim 13, wherein a temperature in the reactionchamber is about 100° C.-600° C.
 19. The method of claim 13, whereinpurging the metal source gas comprises purging the metal source gas fromthe reaction chamber using a purge gas selected from a group of purgegases consisting of argon and nitrogen.
 20. The method of claim 13wherein a pressure in the reaction chamber is about 0.1-10 torr.
 21. Themethod of claim 1, wherein the upper electrode comprises at least onematerial selected from a group of materials consisting of polysilicon, anoble metal, and metal nitride.
 22. The method of claim 21, wherein thenoble metal is selected from a group of noble metals consisting of Ru,Pt, and Ir.
 23. The method of claim 21, wherein the metal nitride isselected from a group of metal nitrides consisting of titanium nitride,tantalum nitride, and tungsten nitride.